Use NULL as parameter when pointer can only be NULL.

Code clarification.

Reviewed-by: Paul Yang <kaishen.yy@antfin.com>
(Merged from https://github.com/openssl/openssl/pull/9514)

crypto/ex_data.c

diff --git a/crypto/ex_data.c b/crypto/ex_data.c
index d7d0d5a..a49aa08 100644
--- a/crypto/ex_data.c
+++ b/crypto/ex_data.c
@@ -421,7 +421,7 @@
     if (f->new_func == NULL)
         return 0;
 
-    f->new_func(obj, curval, ad, idx, f->argl, f->argp);
+    f->new_func(obj, NULL, ad, idx, f->argl, f->argp);
 
     return 1;
 }